Bajabugrotary

Hi guys new to the site, always went in on here to get info and now I’d like to get some info from you guys. I have a street ported 12a running on 48 ida carb jetted to 51 that just failed on me in the desert, did a compression test and a couple rotors were at 62 which is what I was told by my rotary mechanic is low but it didn’t sound like I broke anything big. This motor was already not powerful enough torque wise and I would get stuck in sand alot so I’m upgrading my trans because that went out to have a limited slip instead of super diff and I’m changing my r&p to a lower number because Rancho Transaxles said I would get better low and mid range power which is what I want. My rotary guy said he could build be a 13b na pp and I would make about double the power I’m making now. So should I spend the 4k in rebuilding my 12a to have the same power or spend the extra $$ into a 13b and will I really feel the difference, remember I’m going to any possible more torque, a noticeable amount of power difference and a reliable motor, please help me make my decision. Thank you all.

diabolical1

iTrader: (3)

welcome to the board.

well, if all you want is more power and torque, then get the 13B. just be prepared, it will be far more rowdy in comparison, but i guess if you're racing/driving on sand, it will probably be just fine.

Bajabugrotary

Thank you, appreciate the response, it’s just a desert car but sometimes it goes in the sand and i constantly have to get towed out. I’m hoping the transmission upgrades will help but also if I’m paying 4k to go back to what I had and wasn’t happy with, what’s another 3 grand. I was told by my mechanic that he could put something all together for me to bolt right back into my bug minus paying for a new custom exhaust for just under 7k but my question is will the 13b pp hold up well for multiple seasons, this 12a lasted me 7 years romping on constantly hitting 7-7500 rpm on a regular basis. Does the periferal port take away from reliability? Because I could just street port it to give it more power but be dependable.

Bajabugrotary

For the transmission I’m adding limited slip vs super diff and they’re going to change the ring and king gear ration for more grunt as they explained it. I was also told by multiple companies that the limited slip would help out quite a bit, considering the super diff is z45@ and limited slip is 1600.

Bajabugrotary

And what do you mean by rowdy lol. Super diff is 450

diabolical1

iTrader: (3)

how long do they last? i have no clue. i've never owned one.

that said, i would imagine, as with any engine, it will depend on how you use it and how you care for it. intuitively, if you look at their history, reliability does not seem to be a problem though.

some links:
https://www.rx7club.com/rotary-car-p...engine-170707/

https://www.rx7club.com/naturally-as...arched-982748/

diabolical1

iTrader: (3)

while i've never owned one, i've been around quite a few of them in the past - granted the majority of them were race cars. they're brutally loud without decent muffling. they treat your body like a tuning fork. i ran stock port engines with open headers a few times and yes, they are loud too, but it's just not the same.

i'm guessing since you're sticking it in a Beetle, there's probably not going to be much muffling.

gracer7-rx7

iTrader: (16)

I'd be tempted to just street port the 13b and save some $$. Try to search for some dyno charts and look at the torque and power curves and see how that translates to the RPM you typically use in your driving.

Bajabugrotary

reliability wise and torque wise what would be my best option between street port, bridge port and periferal port. I really need to get some torque out of this swap at least enough to be noticeable and if it’s more powerful then even better I just need to know which way to go quickly. appreciate any advice you can give me. Thanks!

Bajabugrotary

this would be to go to a 13b versus staying with my 12a. From what I have seen doing a turbo on a 12a can be complicated and remember I’m staying with a Weber carb not going fuel injected. So say 4500 too fix my 12a and be unhappy with performance or spend 6-7 and add at minimum 30lbs of torque and I’m pretty sure I would feel that and that’s just going from stock to stock not adding porting or anything else my mechanic can do to get me the most torque. He’s mentioned adding msd to help with throttle response,starting and having a rev limiter but we didn’t get into what could he do to increase my torque he did mention I was tapped out of mods I could do to the 12a without turboing it but I don’t want to deal with a turbo.

gracer7-rx7

iTrader: (16)

More displacement is always a good option for torque, right?
Heck, a stock fuel injected 13b from an FC is north of 150 hp with all the emissions and such. Hard to say no to a 13b swap.
12a parts are hard to find and if you have any good parts left on your engine, I'm sure you can sell them to others.

Bajabugrotary

Sounds about right, appreciate the insight and help. I’m not doing fuel injected, going to stick to my Weber carb setup since this is a car for off-roading and less of a headache wiring wise. I was just quoted 4200 for a 13b rebuilt and setup to be turnkey using some of my old 12a parts minus the intake and exhaust, my 12a and different mechanic told me 2300 plus parts to fix my 12a. Assuming rebuild kit and broken parts are 1500 the extra 1-1500 to get a 13b intake and new exhaust made and get a mild street ported 13b would be well worth it, this guy does it out of his backyard for 20 years and came with a good reputation and his instagram shows the engines he builds and they all look super clean and legit, my original builder who’s an actual shop told me 6-7k for a 13b. That’s why I was so hesitant in making the swap. But now with this new guy and saving that much money I gotta go for it, stock for stock it’s like 30lbs of torque difference and I know I’ll notice that.